Production of refractory metals



Deb. 11, 1956 R. S. HOOD PRODUCTION OF REFRACTORY METALS Filed Feb. 19,1952 IN VEN TOR.

RALPH 6- Hoop- United States l a tent 2,773,759 PRODUCTIUN F REFRACTORYMETALS Ralph S. Hood, Marblehead, Mass, assignor to Monsanto ChemicalCompany, St. Louis, Mo., a corporation of Delaware Application February19, 1952, Serial No. 272,378 Claims. (Cl. 7584.5)

This invention relates to the production of Group IVa metals and moreparticularly to the production of such metals in a high state of purity.

A principal object of the present invention is the provision of animproved process whereby the production of Group IVa metals may beefliciently and cheaply carried out. Another object is to provide animproved process for the production of the said metals which results ingreat savings of energy in the manufacture thereof.

The present invention relates to and is an improvement upon theinvention described and claimed in Findlay application Serial No.200,606, filed December 13, 1950. According to the Findlay invention aGroup IVa tetrahalide in the vapor form is reacted with the vapor of areducing metal, for example, a metal of the alkali or the alkaline earthgroup metals: sodium and magnesium. In the practice of the Findlayinvention, Group IVa metals are produced from the corresponding halidesand preferably the chlorides by mixing said vaporous chlorides with thevapor of a reducing metal, the reaction being characterized by anextremely high temperature. In the Findlay invention the metal may berecovered in the form of a solid ingot, if desired, which issubstantially free of the by-product reducing metal halides formed inthe process by reason of the fact that said by-product halides areformed in the vapor state.

In accordance with the present invention I have discovered that whensaid Findlay process is carried out with a reducing metal of the group:sodium or magnesium, or mixtures thereof, the heat energy required inorder to vaporize said reducing metal may be completely recovereddirectly from the products of the process. Furthermore, vaporization ofthe reducing metal may be practically achieved by rectification of saidby-product vaporous chlorides and said liquid reducing metal or metals.Preferably said rectification is carried out in a zone forming mixedchlorides are obtained in a mixture having a lower duced. Such lowermelting point considerably simplifies by reason of the reduced meltingpoint, the handling of the by-product salt produced in the process.

All or part of the sodium, the magnesium or'any suitable mixture thereofmay be supplied in liquid form to the reactor and vaporized therein.ducing metal or metals is supplied in vapor form, somewhat more heat isavailable for vaporizing that portion of said reducing metal supplied inliquid form. Insofar as ease of vaporization is concerned, I prefer tosupply all of the magnesium for reaction as liquid magnesium. Whensodium is additionally to be used, it is desirable to vaporize thesodium metal externally of the reactor and to supply the sodium vaporsto..the torch in the manner describedin said Findlay application.

Where part of said re-' For a more complete description of the present'inven tion, reference will be made to the following description whenread in connection with the accompanying drawing.

In the drawing the single figure shows, in sectional view, the reactionchamber in which numeral 10 indicates a cylindrical wall defining thereaction zone. The cylindrical wall is provided with a top 11.Surrounding the cylinder 10 is an annular chamber 13 formed by a secondcylindrical wall 12, spaced some distance therefrom. Annular chamber 13is provided with vapor-liquid contact means such, for example, asirregular particles, Berl saddles or a series of bubble plates ofconventional construction. These may be formed of refractory metals suchas titanium or molybdenum. Where loose packing material is employed asthe liquid-vapor contact means, it may be supported upon a screen orperforated plate 15. The upper end of the .cylinder formed by wall 12 isprovided with a cover 16 spaced a distance from plate 11. The lower endof cylinder 12 is provided with a sloping bottom 18 and also with aningot mold 20 located therein. It is also provided with a salt exit pipe21. Upon the outer surface of cylinder 12 there is provided coolingmeans 22 which may take the form of metal tubes through which a liquidmetal such as sodium or'magnesium may be passed. Such means for coolingduring reaction may also be utilized to heat the reaction zone when itis desired to start the process.

Surrounding the outer wall 12 and the cooling tubes 22, is aheat-insulating jacket 24.

A supply conduit for titanium tetrachloride is provided at 25, the endof which terminates within a venturi throat or nozzle 26, the latterbeing attached to and centrally located in cover plate 11. Defiectingvanes or ring 27 are provided for effecting additional vapor circulationwithin the reaction zone.

A circular distributing trough 28 is arranged above the packing 13, saidtrough being supplied with liquid magnesium by means of pipe 29connecting with an outside source of the metal, which source is notshown.

Should it be desired to use sodium metal in addition to the magnesiummetal as a reducing agent in the present process, such sodium ispreferably introduced in the vapor state by means of a separate nozzle.Such separate nozzle is indicated by numeral 31 and is arranged todischarge sodium vapor through an orifice located centrally withinnozzle 26. Nozzle 31 is supplied with sodium vapor by means of pipe 23.

The titanium ingot is indicated by numeral 30 and is formed in mold 20.It is arranged so that it may be withdrawn, which is done at a rate suchthat the growing end thereof is maintained approximately at the samelevel with respect to the position of the flame.

The operation of the described apparatus is carried out as follows. Thereaction-rectification zone is freed of all reactive gases, such as air,by evacuation and replacement with an inert gas which may be argon. Heatis applied to the zone by passing a molten metal such as sodium throughcoils 22 and the temperature thereby raised to about the boiling pointof magnesium, which is 1120 C. Vaporized titanium tetrachloride isadmitted by means of pipe 25 and molten magnesium at a temperature ofabout 1103 C. is admitted by means of pipe 29. The liquid magnesiumflows into distributor trough 28 and then down over the packing 14contained in annular space 13. By contact with the heated packing themagnesium is vaporized, the vapors thereof entering the space betweenplates 11 and 16 and thence entering the space defined by the venturinozzle 26. At this point the magnesium vapors. are mixed and reactedwith the titanium tetrachloride vapors, the latter entering through pipe25. The employment of a venturi nozzle 26, supplied with titaniumchloride vapors by means of pipe 25, resultsin the development of apressure differential sufiicient to overcome the pressure drop of themagnesium chloride vapors through the packing contained in channel 13.

The reaction between the titanium tetrachloride vapors and-magnesiumsvapors results in the formation of titanium metal. andmagnesium: chloride. The reaction so occurring is avhighly exothermicone with temperatures reachinginathe. neighborhood of 2000" C. and thuswell above the melting point. ofthe metal formed duringthe reaction. Themetalformcd in the flame is formed in the molten state and in.relatively small particleswhich are carrieddownwardly by the velocity ofthe hot gases of the flame. These molten particles impinge and adhereupon. the liquid upper surface 19' of ingot 30. In this manner the ingotisformed. In order to maintain the upper surface19 of. ingot atsubstantially the same position in mold 30, the ingot is gradually drawndownwardly into and through the mold.

Simultaneously with the formation of titanium there is also formed thecorresponding, chloride of the reducing metal, namely magnesium and/orso-diumchloride and by reasnof the prevailing high temperatures thissalt is formed in the vapor state. The vaporous salt passes into annularspace 13 where it comes into contact with packing material 14 containedtherein. It also comes into contact with the down-flowing liquidmagnesium, withthe result that rectification with vaporization of themagnesium takes place therein. The magnesium vapors, at a temperature of1120" C., pass into the burner or torch formed'by venturi throat 26.Liquid magnesium chlo-. ride, which is formed by the condensation of thevapors, fiows'downwardly over the packing in a direction counter to theentering magnesium chloride vapors and leaves the reaction zone by meansof pipe 21.

Since all of the titanium metalgenerated in the flame does not adhere tothe ingot surface, some non-adhering titanium is collected in thereaction zone as a finely di. vided powder. Such powder is carried outwith the molten salt flowing through pipe 21. It may be recovered fromthe molten salt by several means, preferably by the means described andclaimed in application Serial No. 252,564, filed October 22,1951, ofwhich-application the present inventor is a coinventor. In saidapplication the titanium powder is separated'from the liquid salt byfiltration. Adhering salt is removed from the powderby washing withaluminum chloride. If desired in the operation of the present process,all of the-titanium may be recovered in the form of a powderrather thanin the ingot form, inwhich eventthe ingot is maintainedin a fixedposition in the mold. In this event the titanium ingot grows to such anextent that the cooling means associatedwith the mold is nolonger.suflicient to conge'al the molten titanium impinging upon the uppersurface thereof with the result that'such titanium flows into the salt,is congealed and removed with such salt.

Ingeneral, when' utilizing an apparatus, such as that described, whichis. provided with eflicient heatinginsulation, sufiicient heat isavailable from the reaction to volatilize all of the magnesium chlorideformed in the process so that the metal may berecovered-in substantiallypure'form. However, with less'efli'cient insulation and, accordingly, agreater heat loss, and particularly Wherethe reaction zone is providedwith cooling means 22, shown in the drawing, :condensationof theby-product salt occurs'and the so-formedfliquid salt collects' inthebottomof the zone; asialreadydescribed. The removal of heat from thereaction zone in the manner shown above results in the formation ofliquid saltwhich contacts with and in part fiows over both wallsdefining space 13, thus cooling the sa'm'e'an'd protecting the materialthereof against the'very hightemperatures produced by flame 17. Theupper part of wall is in contact with the reducing metal, thus both.ends as well as the middle ofjthe wall or cylinder 10'1 defining thereaction zone are cooled by contact with either liquid metal. or salt ormixtures thereof.

By directing the flame downwardly substantially all of the liquidtitanium particles are separated from the vaporous chlorides during thechange in direction thereof prior to entry of the same into thefractionating zone. 5

Having thus described my invention, what I claim is:

l. Aprocessfor producing a Group IVa metal'selected from the groupconsisting of zirconium and titanium which comprises contacting thetetrachlorideof said Group IViz metal with a gaseous reducing metalselected from the group consisting of sodium and magnesium in a reactionzone at a temperature higher than the boiling point of the chlorides ofsaid reducing metal but below the boiling point of said Group IVrz metalwhereby ,condensed Group'IVa metal and vaporous chlorides of saidreducing metal are formed, passingliquid'reducing metal and saidvaporous chlorides into a heat exchange zone in heat exchangerelationship with each other whereby said liquid reducing. metal isvaporized and said .vaporous chlorides are condensed, andpassing saidvaporized reducing metal-into the aforesaid reaction zone;

2. The process of claiml wherein thexGroupIVa meta is titanium andwherein the reducing metal is sodium.

3; The-'process'of claim 1 wherein the Group IVa'metal is zirconium andwherein the reducing metal is sodium.

4. A processfor producing metallic titanium which comprisescontactingtitanium tetrachloride with sodium vaporsinareaction zone ata' temperature higher than the boiling point of sodium'chloridebut'below the boiling point of titanium whereby condensed titanium andva-.

porous: sodiurrr chloride are formed, passing vaporous.

sodiumchlorideupwa'rdly into a heat exchange zone :c'ir- 1ctmiferentiallyssurrounding said re'actionzone, introducing moltensodium downwardly into said'heat exchange zone and indirect heat'exchange'with said vaporous sodium chloride whereby'the molten sodiumis vaporized and the portionof the said 'h'eat exchange zone, andpassing said v sodium vapors :into the aforesaid reaction zone;

5. A process for producing metallic titanium which comprises contactingtitanium tetrachloride'with sodium vapors'ina reaction"zone-maintainedat a temperature between the' meltingpointand" the" boiling point oftitanium, whereby liquid titanium and gaseous sodium chloride areformed,.separating said gaseous sodium chloride-from said liquidtitanium-introducing: said gaseous sodium chloride upwardly into a heatexchange zone circumferentially surroundinglsaid reaction zone,introducing'molten sodium downwardly into said heat exchange zoue'andtindirect heat exchange with said gaseous sodium chloride 7 whereby themolten sodium-is vaporizedand the gaseous v sodium chlorideiswliquified, removingliquidsodium chlo- 1 ride from the'lower portionof said heat exehange:zone,.

removing sodiumv'aporsfrom theupper portion of said heat exchange zoneand passingsaid so'diumvaporsrinto the-aforesaid reaction zone.

References Cited in the file of'this-patent OIHER REFERENCl-ISJournaLof-Metals, April 1950 pages634-640.

1. A PROCESS FOR PRODUCING GROUP IVA METAL SELECTED FROM THE GROUPCONSISTING OF ZIRCONIUM AND TITANIUM WHICH COMPRISES CONTACTING THETETRACHLORIDE OF SAID GROUP IVA METAL WITH A GASEOUS REDUCING METALSELECTED FROM THE GROUP CONSISTING OF SODIUM AND MAGNESIUM IN A REACTIONZONE AT A TEMPERATURE HIGHER THAN THE BOILING POINT OF THE CHLORIDES OFSAID REDUCING METAL BUT BELOW THE BOILING POINT OF SAID GROUP IVZ METALWHEREBY CONDENSED GROUP IVA METAL AND VAPOROUS CHLORIDES OF SAIDREDUCING METAL ARE FORMED, PASSING LIQUID REDUCING METAL AND SAIDVAPOROUS CHLORIDES INTO A HEAT EXCHANGE ZONE IN HEAT EXCHANGE RELATIONSHIP WITH EACH OTHER WHEREBY SAID